1. Field of the Invention
The present invention relates to a fuel cell comprising electrolyte electrode assemblies, together with a first separator and a second separator sandwiching the electrolyte electrode assemblies therebetween. Each of the electrolyte electrode assemblies includes an anode, a cathode, and an electrolyte interposed between the anode and the cathode. Further, the present invention relates to a fuel cell stack formed by stacking a plurality of such fuel cells.
2. Description of the Related Art
Typically, a solid oxide fuel cell (SOFC) employs an electrolyte made up of an ion-conductive solid oxide, such as stabilized zirconia. The electrolyte is interposed between an anode and a cathode to form an electrolyte electrode assembly (MEA), and the electrolyte electrode assembly is sandwiched between separators (bipolar plates). In use, a predetermined number of MEAs and separators are stacked together to form a fuel cell stack.
In the fuel cell stack, a fuel gas such as a hydrogen gas and an oxygen-containing gas such as air are supplied to the anode and the cathode of the electrolyte electrode assembly. It is required that the fuel gas and the oxygen-containing gas be supplied to each of the fuel cells.
For example, in the fuel cell disclosed in Japanese Laid-Open Patent Publication No. 2002-203579, as shown in FIG. 8, power generation cells 1 and separators 2 are stacked alternately. A first end plate 3 and a second end plate 4 are provided at opposite ends of the fuel cell in the stacking direction. Each of the power generation cells 1 includes a fuel electrode layer 1a, an air electrode layer 1c, and a solid electrolyte layer 1b interposed between the fuel electrode layer 1a and the air electrode layer 1c. 
A fuel supply channel 5a and an air supply channel 6a are formed in the separators 2. The fuel supply channel 5a and the air supply channel 6a extend from the outer circumferential surface of the separator 2 substantially toward the center of the separator 2. An end of the fuel supply channel 5a is connected to a fuel hole 5b, and an end of the air supply channel 6a is connected to an air hole 6b. The fuel hole 5b opens at a substantially central position of the fuel electrode layer 1a of the power generation cell 1, and the air hole 6b opens at a substantially central position of the air electrode layer 1c of the power generation cell 1, to thereby form a fuel gas channel 5 and an air channel 6, respectively.
The first end plate 3 includes an air channel 7 having an air supply channel 7a and an air hole 7b. The second end plate 4 includes a fuel channel 8 having a fuel supply channel 8a and a fuel hole 8b. 
However, in the conventional technique, since the fuel gas channel 5 and the air channel 6 are formed inside of the same separator 2, a sealing structure between the fuel gas and the external atmosphere, a sealing structure between the air and the external atmosphere, and a sealing structure for blocking flows between the fuel gas and the air, are required. Therefore, the sealing performance tends to be low, the structure of the separator 2 is complicated, and the cost for producing the separator 2 is high.
Further, in the fuel cell, since the separator 2, the first end plate 3, and the second end plate 4 are provided, three different separator bodies are required. Thus, overall production costs for the fuel cell are high.